Phoenyx Fitness, New York

Malenna Saunders grabs her ROTC and Air Force experience by the horns when she leads intense indoor and outdoor boot-camp or fitness classes. Warrior boot camp prepares patrons to slay unwanted fat during a 60-minute romp through plyometric and cardio conditioning melded with strength training and calisthenics routines, and Bowery Babes boot-camp sessions cater to moms or three toddlers standing on one another's shoulders dressed as a mom. Meanwhile, kettlebell workouts and functional exercises tone everyday muscles.

Certified instructors helm other group fitness classes, such as Vinyasa yoga and Zumba cardio-dance classes, within studios fully stocked with workout-enhancing props. Patrons of all fitness levels shimmy into Zumba sessions to hip-shake away excess poundage, mastering easy-to-follow Latin dance moves, which can add spice to tired chimney-sweeping routines.